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<html lang="en">
  <head>
    <meta charset="UTF-8" />
    <meta name="viewport" content="width=device-width, initial-scale=1.0" />
    <title>Document</title>
  </head>
  <body>
    <img src="images/s.gif" alt="" />
    <div>上午好</div>
    <script>
      var img = document.querySelector("img");
      var div = document.querySelector("div");
      var date = new Date();
      var h = date.getHours();
      if (h < 12) {
        img.src = "images/s.gif";
        div.innerHTML = "上午好";
      } else if (h < 18) {
        img.src = "images/x.gif";
        div.innerHTML = "下午好";
      } else {
        img.src = "images/w.gif";
        div.innerHTML = "晚上好";
      }
    </script>
  </body>
</html>
